BARN OWLS


Tyto alba

INTRODUCTION

Nocturnal

Barn owls are terrestrial and are common around the world and are found on all continents, except Antarctica.

They are 29 to 60 centimetres  in length and have a wingspan of close to I metre.

They don't hoot like other owls, instead they make a raspy hissing or  shrieking sound.

Barn owls have a very distinctive heart shaped face.

HABITAT

Barn owls are found on nearly all the continents excluding the poles and desert environments.

They can live in a variety of habitats including grasslands, crops and open and riparian woodlands.

The barn owls can be found roosting in cavities such as roofs, hollowed trees, small caves and small gaps but will lay their eggs on bare wood or stone.

The habitat puts little pressure on the owls and they find the food they need and they can live in almost any area in their environment.


MATING

Barn owls cross-fertilise with the opposite sex and have internal fertilisation.  

Males will attract a female with a call and then chase the female. The male and female will make a series of calls before mating.

The eggs protect the owlet which is inside. If one parent dies hunting, the owls will still hatch and the other parent will hunt for them. The owls use viviparity, so the unhatched owls will die if the mother dies.

REPRODUCTION

For owls, their reproductive organs are neatly and internally tucked away. Males manage to fertilize the female by rubbing the opening under their tail against hers to transfer a tiny drop of sperm onto the surface. Then the sperm swims up a long tube to fertilize the egg. The barn owl uses oviparity and lays eggs. 

The female barn owl lays five to ten eggs but can lay up to 15 at a rate of one egg every two to three days. More eggs are laid when food is plentiful because the female is at her healthiest and it is likely more young will survive when food is plentiful. The owlets will hatch after 32-34 days  and can hunt on their own after 2 months. As the barn owl has a life expectancy of only about two years, females often have two broods a year.  The young grow to full adulthood rapidly and many breed in their first year at around ten months old.

Advantages include the fact that both parents hunt for the food but barn owls may never meet a mate but this is unlikely because they are quite common. This strategy works very well.

PARENTAL CARE

The parental role is shared. The male gathers the food, (but sometimes the female can) while the females do the incubating and brooding, joining in food collection when the young may be left. This does mean that the nesting can fail if either parent dies before the young can be left uncovered (around 3 weeks after hatching). The baby barn owls are able to eat their own body weight in food every night. Barn owls use "K" selection and the survivul rates are 30%.

Their strategy works well for them but it has low survival rates.

The owl below is nesting the eggs. She will stay on her eggs until they hatch and the young can stay uncovered ater 3 months. The male will hunt because if the eggs are left uncovered they could die. If the male dies the babies might very likely also die because of lack of food. There is medium parental care because of the two parents;
the male gathers the food, while the females do the incubating and brooding, joining in food collection when the young may be left.

Barn owl nesting

Bibliography

 

Birds of Prey - Majestic Masters of the Sky. (2007).
  Parragon Publishing.


 

Melbourne's Wildlife - A field guide to the fauna of Greater Melbourne. (2006). Melbourne:
  Museum Victoria, CSIRO.


 

Field Guide to the Birds of Australia.  (2004). Simpson & Day.
 
Penguin, Viking.


 

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